This invention relates generally to electrical devices such as multi-part plug and socket assemblies, switches, feed through, test leads, signal wires, and relays, and more specifically relates to electrical devices that incorporate an antenna-effect inhibiting feature to protect the signals carried by the device from electromagnetic interference.
The invention related further to protecting electrical circuits from receiving electromagnetic interference which might be induced in conductors leading to the electrical circuit. More specifically the invention relates to electrical connectors which provide for suppression of electromagnetic interference by means which form part of the connector itself or as an accessory thereto.
It is known that electrical signals carried by connectors, or adjacent apparatus, may be subject to electromagnetic interference as the result of induced signals picked up from the radiation of adjacent electrical equipment, such interference results from leads acting as an antenna that senses stray electromagnetic radiation; accordingly, the sensing of stray signals in this manner is known as the "Antenna-effect". Various efforts have been made to avoid or suppress the result of the antenna-effect, but such efforts have been found to be inconvenient and/or expensive to implement, or both.
For example, it has been found in the past that antenna-effect stray signals can be avoided by encapsulating leads in sheaths of magnetic-shielding sheet material, or by determining the strength of nearby stray signal fields and then moving all such nearby sources to a physical distance from the leads that has been calculated to prevent the possibility of undesired signals being picked up by electromagnetic induction. It can be seen, readily, that such preventive methods and techniques are indeed costly and inconvenient. Other attempts to reduce or avoid antenna-effect stray signals have involved the use of ferrite cores. However, until now such uses have required additional circuit elements, such as insertion of a jumper cable, having a permanently included ferrite core, in series with the main conductors in the circuit; or, awkwardly and inconveniently surrounding one or more of the circuit conductors with separately applied ferrite cores.
It is established practice, in industries that make use of thermocouple sensors, to couple the sensor into a related electrical circuit by means of an electrical connector. When for example thermocouples are connected to instruments such as panel meters, controllers and transmitters, the input signal from the sensor or transducer usually travels substantial distances along fine gauge electrically conductive wire leads. The length and nature of such leads and the environment in which they must function often create conditions that favour occurrence of the antenna-effect. In many cases, the leads or signal wires from a sensor or thermocouple are first attached, for convenience, to an electrical connector, for coupling to an instrument or the like. As soon as the conductors of the connector are electrically coupled to the circuit, a potential antenna is created. Of particular importance are thermocouple connectors which are particularly susceptible to the antenna-effect because of the long lead conductive path of the conductors themselves and the high input impedance of the instrumentation.
This invention applies to the fields of use wherein there is necessity for including an electrical device in a low level signal circuit, e.g. a thermocouple sensor, and provides, a new apparatus for eliminating undesired electromagnetically-induced stray signals.
Accordingly, it is an object of this invention to provide means associated with an electrical device that is capable of removing stray signals that may be induced in the leads of the device.
It is another object of this invention to provide an apparatus for eliminating the effects of undesired stray signals in circuits, that is uncomplicated in design, and that is simple and relatively inexpensive to produce.
It is still another object of this invention to provide means associated with an electrical device for eliminating the effects of undesired stray signals in its circuits, that is easily adaptable to single-wire or multi-wire connections.
Another and further object of this invention is to provide means associated with an electrical device for eliminating the effects of undesired stray signals in its circuits, that can be manufactured easily in various configurations to accommodate differing circuit requirements.
And yet another and further object of this invention is to provide means associated with an electrical device for elimination of the effects of undesired stray signals in its circuits in which operative elements of the device may be configured to facilitate insertion and removal of wire conductors.
Other objects are to provide:
(A) In an electrical device e.g. a plug and socket, a switch or a relay, which includes two contact members with respective surfaces, for bringing into contact to establish an electrical connection, antenna-effect inhibiting means disposed adjacent to the connection surface of at least one said contact member. PA1 (B) An electrical device wherein said antenna-effect inhibiting means is a ferrite element, as defined herein. PA1 (C) An electrical device wherein said at least one contact member is one part of a multi-part plug and socket connector. PA1 (D) An electrical device wherein said antenna-effect inhibiting means is incorporated with said device. PA1 (E) An electrical device wherein said antenna-effect inhibiting means is a module separably incorporated with said device, or attachable thereon. PA1 (F) An electrical device wherein said antenna-effect inhibiting means surrounds said connection surface, and particularly may be a multi-part element assemblable about said connection surface. PA1 (G) An electrical device wherein said antenna-effect inhibiting means is incorporated in said one contact member, or forms a housing for said at least one contact member.
In another form the electrical device includes two or more discrete contact members with respective surfaces for bringing into contact to establish an electrical connection, and has respective antenna-effect inhibiting means disposed adjacent to the respective connection surface of each said contact member.
A feature of this invention is the provision for association with an electrical device of a signal inhibiting ferrite element that surrounds a wire lead intended for connection in a circuit, so as to prevent the propagation of stray signals through the device to undesired parts of the circuit.
The term "ferrite", as commonly understood in the electronics field, denotes a particular material having one or more oxides of iron in particulate form in a carrier such as a plastics material. This usage of the term "ferrite" is to be distinguished from the usual dictionary definition which is a generic name for a number of oxides of iron. In this specification, the term "ferrite" is to be understood as including within its scope any suitable material having an absorption and/or shielding effect as concerns electromagnetic waves which may be emitted at or adjacent to a zone of completion of an electrical circuit. Known ferrite elements consist of ferrite material sintered into a convenient shape. Other known "ferrite" materials for the suppression of electromagnetic interference are nickel-zinc compositions and manganese-zinc materials, of different compositions to permit selection of an optimum type for a given application; pressed parts, components, and powders are known.
It has been found that ferrite elements, when properly included in an electrical circuit, act as an electromagnetic "sponge" to absorb the unwanted electromagnetic wave energy and to reduce or eliminate the antenna-effect of the conductors with which the ferrite elements are associated.
These and other and further objects, features and advantages of this invention will be made apparent to those having skill in this art, by the following specification considered with reference to the accompanying drawings, in which: